I did my first all grain batch on my new system which is a single tier RIMS and Honeywell controlled HLT. I was only able to get 66% efficiency and I think it was somehting to do with my batch sparge process.

With this false bottom I have 3 gallons of foundation water. Which is really putting me off in my calculation. This was my process for my batch sparging that day.

 Used a 1.25 to 1lb grain ratio
 Filled the mash tun with 3.25 gallons of foundation water to cover the false bottom
 Then added 3.75 gallons on top of that to achieve my water to grain ratio
o This totaled out to be 7 gallons
 Heated the 7 gallons to 154F
 Doughed in and stirred so no dough balls were there
o Let sit for 10 minutes
 Began to re-circulate at a slow rate controlling the flow back into the tun via a ball value on the outside of the RIMS Tube.
 Stirred at 30 minutes
 Stirred at 50 minutes
 Stirred at 60 minutes
 Batched out at 1 hour 10 minutes
 Drained completely including all foundation water  NEED HELP ON THIS STEP

SECOND BATCH SPARGE

Next I filled the Mash Tun back up but only with 4.5 gallons. So not all the grains were covered. My issue here was because of the false bottom I basically need to fill again with an extra three gallons to get coverage but I didnt. I was confused about how this would effect the overall dilution of the sugars left in MLT in turn bringing the gravity down and giving me way more water then I needed. So my grains were fully covered with water.
 I stirred and let sit for 10 minutes
 Began re-circulating again about 10-15 minutes
 Pulled the amount needed to fill the boil kettleI should have hit 1052 for my OG instead hit 1044. I my pre-boil gravity was 1031.
I think I have to switch to fly sparging because of the false bottom.PLEASE HELP!!!!

wow! That's quite a resevoir down there. I use a similar design from Sabco, and it gives me about two inches at the bottom of the keggle.

You're doing RIMS so you are recirculating the wort. If you had a sparge arm which would spray the entire grain bed, you could get away without submerging the grain.

Just FYI, with my false bottom and RIMS (and batch), I tend to mash wet so that I can get a swirl effect. So I usually mash at 1.3-1.4 quarts per pound. The recirc effect compacts the grain bed below the water level pretty quickly and allows it to be submerged...You should be able to do the same thing.

I routinely get 73% efficiency from my rig.

added after my initial post: Get the Sabco false bottom and make the guy eat his hat...I promise it works great.
Call the mfr of your false bottom and describe what's happening, maybe they have a suggestion.

Thanks for the response! I know I have considered getting a different false bottom. I talked to the mfr and he was really nice. Says he uses himself and is getting 85% efficiency off fly sparging. So I 'm going to try this on Saturday. Its just tough with that much extra water.

Not using tri-clamps...just SS 2-way Ball valves on each vessel, then using 2 3-way SS valves for the central plumbing which connects the vessels in to the pump and uses 1 output for HLT to MT and HLT recirc, then Boil to chill.

I love the idea of using tri-clamps for the heating element in the RIMS tube so that you can easily remove for cleaning. I may go that route eventually. I know my element is sludgy.

@Bryce, I have the same false bottom as you (PICO) and have been fly-sparging with 80%+ efficiency (my system is a direct fired recirculation mash so the Pico's extra space between the bottom of the mashtun and the false bottom/grain is good). However, I was thinking of moving over batch sparging (to save time) and also was concerned about the "dead space" below the false bottom with this technique. I'm thinking of just upping my grain bill to make up for the efficiency loss (something you might consider). Gonna take a few brews to figure out the percentage increase, wish me luck.

I guess I just don't see the point of this design when mounting below the drain and using a siphon tube would reduce this slack space considerably. Mine only needs 7/8ths of a gallon to hit the FB. Frankly, on a NON direct fired tun, I'd put a bottom drain in and rest that pico FB directly on the bottom of the keg (no supports).

I about 20 batchs through now and have it dialed in at 75% percent eff. with a hybrid approach. I fy sparge but only for 20 minutes and always stop earlier enough to account for the 2.5-3 gallons of space below the bottom that will be drained off after the fact into the kettle. Biggest thing that help be was my own grinder and putting in some cross-hatching at the halfway point.

I guess I should clarify my use of "dead space" as being liquid below the grains/false bottom (I have a dip tube and can drain the mashtun almost completely dry and/or recirc). Basically.. if batch sparging with my setup it becomes challenging (in my mind) to get the water volumes right (e.g. 5 gallon batch.. beersmith thinks I need to sparge with 3.5 gallons.. if I put 3.5 gallons in my MT then I only have grains touched by 5 gallons).
@BobbyM , what false bottom do you use in your direct fired MT? I couldn't figure out your MT setup looking at your videos, etc. (BTW- my keggles all have your gear/products on them ) )

I have all keggles if you look at my gallery my setup is posted there. Same as you I have the dip tube below my false bottom. I use a 1 quart to 1 pd ratio for all my beers. So I have thicker mashes since I have to add more water than usual to the mlt. I also do RIMS so I should point out I 'm always recirculating. I dough in and rest for 10 minutes at single infusion temp. Start recirculating and then will cross hatch not stir at the 30-35 minute mark for a 60 minute infusion. I start mash out at 50 minutes where I will cross hatch again if its a high gravity brew. Raise temp to 168-170 and begin sparging. However before I start sparging I drain off about 1.5-2 gallons of the mlt so there is just about 1/2 above the grain bed. I then start sparging for 20 minutes. I stop and the drain the remaining 3 gallons into my kettle for a total of 13-14 gallons for a 12 gallons batch.

I will cross hatch at 15 minutes and 45 minutes in if its a high gravity. I have found by subtracting a single cross hatch I can change eff. anywhere from 2-5%. I always try to be nothing above 80% and nothing below 75%.

So just to be clear I fly sparge using the sabco method through a single silicon tube not fancy sprinklers or anything.